1. Field of the Invention
The present invention relates to a centrifuge rotor and in particular to a centrifuge rotor fabricated from a plurality of stacked laminated arms.
2. Description of the Prior Art
The trend in the fabrication of rotatable structures has been away from the use of conventional homogeneous materials, such as aluminum or titanium, and toward the use of reinforced fiber composite structures. Such structures are advantageous because they provide an increased strength-to-weight ratio with its attendant advantages over the conventionally fabricated homogeneous structures.
Presently, a typical use of such composite rotatable structures is found in the area of energy storage devices, such as fly wheels. Exemplary of various alternate embodiments of such reinforced fiber composite rotatable structures are those shown in U.S. Pat. No. 4,458,400 (Friedericy et al., composite material flywheel hub formed of stacked fiber-reinforced bars). U.S. Pat. No. 3,672,241 (Rabenhorst, rotary element formed of layered strips of anisotropic filaments bound in a matrix), U.S. Pat. No. 3,698,262 (Rabenhorst, rotary element having a central hub with a multiplicity of anisotropic filaments). U.S. Pat. No. 3,737,694 (Rabenhorst, stacked discs of hub lamina each carrying an array of bent anisotropic fibers). U.S. Pat. No. 3,884,093 (Rabenhorst, fly-wheel fabricated of sector shaped members centrally connected to a hub, the thickness of each element being greater in the center than at the ends), and U.S. Pat. No. 4,028,962 (Nelson, fly-wheel fabricated of anisotropic material in a disc shape with the central portion of the disc being thinner than the edges).
The use of reinforced fiber material has also been found in other rotating structures, such as rotor blades and tooling. Examplary of such uses are those shown in U.S. Pat. Nos. 4,038,885 (Jonda) and 4,255,087 (Wackerle, et al.). U.S. Pat. No. 3,262,231 (Polch) discloses the utilization of strands of high-tensile strength material, such as glass, as internal reinforcement of rotatable articles such as abrasive wheels.
In the area of centrifuge rotors the art discloses attempts to increase the strength-to-weight ratio. For example, U.S. Pat. No. 2,447,330 (Grebmeier) discloses an ultracentrifuge rotor formed of a metal material which is provided with slots which reduce the weight of the rotor. U.S. Pat. No. 3,248,046 (Feltman et al.) discloses a fixed angle centrifuge rotor formed by winding layers of glass material onto a mandrel. U.S. Pat. No. 4,468,269 (Carey) discloses a rotor with a plurality of rings surrounding a bowl-like body portion.
When using reinforced fiber materials it is advantageous to be able to arrange the fibers so that the maximum strength of the fibers is oriented in a direction parallel to the direction in which maximum centrifugal stress is imposed on the fibers. That is, it is advantageous to be able to provide a spatial relationship of fibers that extends radially outwardly from the central axis of rotation. Most beneficially advantageous is to orient the fibers such that each fiber passes as close as possible through the rotational axis of the structure.
The structure disclosed and claimed in copending U.S. patent application Ser. No. 684,937, filed Dec. 21, 1984 in the names of Popper and Cole and assigned to the assignee of the present invention overcomes the perceived disadvantages of the prior art by providing a rotor using a wound rotor arm. A plurality of wound arms are formed into tiers and the tiers are stacked upon each other.
In view of the foregoing, it is also believed advantageous to provide a centrifuge rotor utilizing a laminated structure arm that facilitates both the placement of sample containers onto the rotor and the mounting of the rotor structure onto its drive and that also enhances the distribution of loads carried at the ends of the rotor into and throughout the entire rotor structure.